Field
Exemplary embodiments relate to a piston pump for a brake, which is capable of increasing a discharge rate of the pump by allowing both an outer piston and an inner piston to be operated when low pressure is applied to an outlet, and reducing a load applied to a motor by allowing only the inner piston to be operated when high pressure is applied to the outlet.
Discussion of the Background
In general, a piston pump for a vehicle brake discharges brake oil at a wheel side to a master cylinder when reducing wheel pressure. Conversely, a piston pump for a vehicle brake discharges the brake oil at the master cylinder side to the wheel side when increasing wheel pressure. An operation of the piston pump for a brake is performed as follows. The brake oil flows into an inlet, and an inlet ball is opened. When the brake oil flows into the sleeve, the inlet ball is closed. By an operation of a motor cam, a piston is moved forward to the opposite side of the cam, and an outlet ball is opened. The brake oil is discharged to an outlet through an orifice. Meanwhile, in order to discharge a large amount of brake oil per time, the piston pump for a brake may increase discharge volume by increasing an outer diameter of the piston, and may increase a discharge amount of the pump by improving performance of a motor.
However, in a case in which the outer diameter of the piston of the piston pump for a brake is increased, there are problems in that high pressure is applied to the outlet of the pump as the outer diameter of the piston is increased, and a pressure load applied to the piston of the pump is increased, such that a high load is also applied to the motor, and as a result, durability of the motor deteriorates. Because a capacity of the motor needs to be increased in order to improve performance of the motor, there is a problem in that price and weight of the motor are increased.
For example, Korean Patent Application Laid-Open No. 10-2014-0104441 discloses “Piston Pump for Vehicle Brake System”.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.